1. Field of the Invention
This application pertains to the planning and design of wireless networks, and particularly to wireless networks which provide or enable high speed downlink packet access.
2. Related Art and Other Considerations
In a typical cellular radio system, mobile terminals (also known as mobile stations and mobile user equipment units (UEs)) communicate via a radio access network (RAN) to one or more core networks. The user equipment units (UEs) can be mobile stations such as mobile telephones (“cellular” telephones) and laptops with mobile termination, and thus can be, for example, portable, pocket, hand-held, computer-included, or car-mounted mobile devices which communicate voice and/or data with radio access network.
The radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by a unique identity, which is broadcast in the cell. The base stations communicate over the air interface (e.g., radio frequencies) with the user equipment units (UE) within range of the base stations. In the radio access network, several base stations are typically connected (e.g., by landlines or microwave) to a radio network controller (RNC). The radio network controller, also sometimes termed a base station controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
Wireless network design is usually performed by means of a computer based planning tool. Several different radio access technologies can be used for building wireless networks, such as frequency division multiple access (FDMA), time division multiple access (TDMA), and code-division multiple access (CDMA). The computer based planning tools of today are capable of planning one or more of these technologies, one at a time, and may also be capable of co-planning two or more networks using the same technology or different technologies.
Computer based wireless network planning tools use digital terrain data to predict radio wave propagation, which is needed to estimate the radio coverage of the projected radio base stations. The traffic load at every radio base station can be input by the planner and/or estimated from geographic and demographic information. The planning tool then predicts the resulting quality of service and traffic capacity in each radio base station for the wireless speech and data services. The prediction can be performed by means of a combination of calculation, table look-up and simulation. The predicted quality of service and capacity is used for testing and optimizing the wireless network design.
Computerized wireless network planning for a CDMA is disclosed in U.S. Pat. No. 5,710,748 to Soliman et al. (which is incorporated by reference herein). Other examples of network planning include the following US patents (all of which are incorporated by reference herein):
6,985,7356,975,8666,973,6226,971,0636,952,1816,940,8386,934,5556,925,0666,917,8166,892,0736,871,0736,850,9466,842,7266,842,4826,810,2466,785,5476,721,7696,711,1486,640,0896,639,9046,636,7436,631,2676,628,9446,556,8326,549,7816,539,2286,505,0456,487,4146,477,1556,466,7976,456,8486,445,9126,360,0986,356,7586,356,5316,246,8806,216,0106,205,2206,173,0676,188,3546,169,8816,111,8575,963,867
In wireless networks based on CDMA, there is a complex interaction between wanted signals and interference, which usually makes a simulation necessary. The simulation involves several random trials, each with a different random distribution of the mobile terminals over the geographic area that is covered by the projected radio base stations. This is known as a Monte Carlo simulation.
To analyze a network based on CDMA, a wireless network planning tool usually performs the following steps.
Step 1. Define the wireless network including sites, cells, antennas, propagation models, and terrain data (digitally input)
Step 2. Predict the radio wave propagation from the base station antennas to the map bins (area units).
Step 3. Input or calculate the total output power and the received interference level, expressed as noise rise, for all cells. This can be done in several alternative ways as described below.
Step 4. Calculate the forward channel received desired power and interference values for all bins in the planned area, as well as the required reverse channel power for a hypothetic UE (user equipment) located in every bin. From these values, plots are generated for showing, for example, common pilot channel signal quality, forward and reverse channel coverage probability, and achieved data rate for different services in the bins.
Step 5. Calculate various data for the cells, such as average output power, noise rise, and forward and reverse channel load. Statistics are developed for the cells and for the planned area.
There are several methods to set or calculate the output power and noise rise values for the cells. The methods typically include (1) setting values for cells manually (e.g., via a graphical user interface (GUI)); importing total output power and noise rise values for the cells from a file (the values in the file may be derived from measurements or from a calculation tool, or may have been entered manually); estimating the values using table look-up; or estimating the values by Monte Carlo simulation.
As mentioned above, according to one method the total output power and noise rise values in all cells can be calculated by the wireless network planning tool from look-up tables. The input to the tables is the estimated traffic in the cell, which is calculated over the bins belonging to the cell. A bin can be considered to belong to the cell with the lowest pathloss or strongest received signal, as seen at the bin. To estimate the traffic in a cell, the expected forward and reverse channel traffic densities in the bins belonging to the cell are taken into account. The look-up tables are thus used to transform the traffic values into output power and noise rise values. Look-up tables for this purpose can be derived from measurements, simulations, or analytical calculations.
The Monte Carlo simulation method (also mentioned above) is intended to simulate a number of different random trials, each representing a possible random distribution of the traffic in the wireless network. In each trial, the UEs are spread over the planned area to simulate forward link and reverse link traffic load, using a random distribution function that gives a UE density equivalent to the desired average traffic intensity. Initial output power values and initial noise rise values are set for the cells, and these values used to calculate initial values for the interference received in the UEs. Each UE is connected to the best serving cell or cells (in soft handover), according to a ranking criterion such as lowest pathloss or highest received signal strength. The output power needed for the voice and data services in the cells is calculated, taking the interference at the UEs into account and adding the common channel power in every cell. The output power needed for the UEs is calculated, taking the noise rise values in the best serving cells into account. The received interference in the UEs is then calculated, as is the noise rise in the cells. Iterations are repeated until convergence is reached. Output, in the form of plots and statistics reports, can be generated from average values and statistical analysis of the simulation results.
The latest evolution of wireless networks comprises the use of the radio carrier for a high-speed data service. Characteristic for this kind of high-speed data service is that it adapts the data rate to the available transmitter power and the radio environment, rather than adapting the transmitter power to the radio environment, which would be necessary to maintain a constant data rate. The speed adaptation usually involves the selection of different modulation and/or coding schemes.
For GSM networks (based on the TDMA technology), the high-speed data service is known as GPRS and EGPRS (GPRS using EDGE). See, for example, Granbohm and Wiklund, GPRS—General packet radio system, Ericsson Review, No. 2, 1999, which is incorporated herein by reference.
For wireless networks based on the CDMA technology, the radio carrier may be used only for the high-speed data service, or may be shared between the high-speed data service and other wireless services. The first principle is implemented as cdma2000 EV-DO (evolution-data only), while the second principle is implementated either as cdma2000 EV-DV (evolution-data and voice) or WCDMA HSDPA (wideband CDMA high-speed downlink packet access). In these implementations, the network contains a traffic scheduling function that allows the high-speed forward (downlink) channel to be time-shared by several users. See, for example, Langer and Larsson, CDMA2000—A world view, Ericsson Review, No. 3, 2001; and Skold, Lundevall, Parkvall and Sundelin, Broadband data performance of third-generation mobile systems, Ericsson Review, No. 1, 2005, both of which are incorporated herein by reference.
In High Speed Downlink Packet Access (HSDPA), multiple users provide data to a high speed channel (HSC) controller that functions as a high speed scheduler by multiplexing user information for transmission over the entire HS-DSCH bandwidth in time-multiplexed intervals (called transmission time intervals (TTI)). The HSDPA system provides, e.g., a maximum data rate of about 10 Mbps. HSDPA achieves higher data speeds by shifting some of the radio resource coordination and management responsibilities to the base station from the radio network controller. Those responsibilities include one or more of the following: shared channel transmission, higher order modulation, link adaptation, radio channel dependent scheduling, and hybrid-ARQ with soft combining. In shared channel transmission, radio resources, like spreading code space and transmission power in the case of CDMA-based transmission, are shared between users using time multiplexing. A high speed-downlink shared channel is one example of shared channel transmission. One significant benefit of shared channel transmission is more efficient utilization of available code resources as compared to dedicated channels. Higher data rates may also be attained using higher order modulation, which is more bandwidth efficient than lower order modulation, when channel conditions are favorable.
High Speed Downlink Packet Access (HSDPA) is described, e.g., in 3GPP TS 25.435 V6.2.0 (2005-06), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; UTRAN Iub Interface User Plane Protocols for Common Transport Channel Data Streams (Release 6), which is incorporated herein by reference in its entirety. Also incorporated by reference herein as having some bearing on High Speed Downlink Packet Access (HSDPA) or concepts include: 3GPP TS 25.425 V6.2.0 (2005-06), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; UTRAN Iur interface user plane protocols for Common Transport Channel data streams (Release 6); and 3GPP TS 25.433 V6.6.0 (2005-06), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; UTRAN Iub interface Node B Application Part (NBAP) signaling (Release 6).
High Speed Downlink Packet Access (HSDPA) is also discussed in one or more of the following (all of which are incorporated by reference herein in their entirety):
U.S. patent application Ser. No. 11/024,942, filed Dec. 30, 2004, entitled “FLOW CONTROL AT CELL CHANGE FOR HIGH-SPEED DOWNLINK PACKET ACCESS”;
U.S. patent application Ser. No. 10/371,199, filed Feb. 24, 2003, entitled “RADIO RESOURCE MANAGEMENT FOR A HIGH SPEED SHARED CHANNEL”;
U.S. patent application Ser. No. 11/292,304, filed Dec. 2, 2005, entitled “FLOW CONTROL FOR LOW BITRATE USERS ON HIGH SPEED DOWNLINK”;
PCT Patent Application PCT/SE2005/001247, filed Aug. 26, 2005;
PCT Patent Application PCT/SE2005/001248, filed Aug. 26, 2005.
Existing wireless network planning tools do not properly model the simultaneous use of a radio carrier for services based on CDMA and a high-speed data service with a traffic scheduling function. Therefore, the existing tools do not accurately estimate the impact of the high-speed data channels on the quality of service and traffic capacity of existing CDMA based services. Moreover, the tools do not accurately estimate the quality of service and the capacity of the high-speed data channel itself. This means that the tools cannot properly analyze wireless networks using cdma2000 EV-DO, cdma2000 EV-DV or WCDMA HSDPA.
What is needed, therefore, and an object of the present invention, are tools, methods, and techniques for designing, testing, and/or optimizing networks with high speed data channels.